SpaceX Plans To Land A Rocket On This Barge

The company has landed on water from altitude before and firm ground in tests. But landing from altitude on a floating platform -- what won't be tethered to anything -- presents a challenge. The eventual landing spot -- referred to as the autonomous spaceport drone by SpaceX but known to others as a, err, barge to most -- measures 91m by 30m. The rocket is 21m wide. SpaceX ackowledges that, pegging their chances of success at around 50 per cent "at best". It goes on to describe the size of the challenge:

At 14 stories tall and travelling upwards of 1300 m/s (nearly 1 mi/s), stabilizing the Falcon 9 first stage for reentry is like trying to balance a rubber broomstick on your hand in the middle of a wind storm.

But a challenge is a challenge, and in this case it will at least be mercifully broken down to make it at least vaguely plausible. First, a boostback burn will get the craft headed in the right direction; a second 'supersonic retro propulsion' will slow the rocket to 250m per second; and a final landing burn will slow it to about 2m per second. Chief among the mechanisms to the make the final landing smooth are SpaceX's

hypersonic grid fins, which finely control the direction of the Falcon 9 before it bumps down on Earth. Good luck, SpaceX -- this time, it sounds like you might need it. [SpaceX via Engadget]